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426

Deflection of Helical Springs.

Deflection of Helical Springs.This may be found by
imagining the wire uncoiled, and treated as a straight shaft.
Let / = length of wire from A to B, and n  number of coils in
that length (Fig. 379).

cf. 380.

.
n,    andA=

2 /slbs lr
-

,.
64

N.B.  This is for round wire only.    For square wire,

wn

60*5

and for rectangular wire,           wnr*

_____          //,/. 845.)

The above formulae have been thoroughly tested for steel with
C = 12,000,000 Ibs. and found reliable with that value. The curve
of work during extension or compression is found as for a bar
(page 367).

Bending Stress-Action.Fig. 381 represents a model
devised by Prof. Perry to shew the stresses occurring in a beam.
Supposing W very heavy and beam / so light as to be negligible,